JPH03228326A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to form a SOI substrate provided with a semiconductor layer, which has a good crystal quality and is thin, by a method wherein the thickness, at an arbitrary position, of a first silicon substrate ground to a constant thickness is measured by a laser interferometric thickness measuring device, the thickness at other arbitrary position is ground by a grinder with pressing force being adjusted, the grinding and the measurement are repeated. CONSTITUTION:In the manufacturing method of an SOI substrate 5 with a process, wherein a second silicon substrate 2 is laminated on a first silicon substrate 1 via an insulating film (a SOG film) 3 and the substrate 1 is ground to form a thin silicon layer 13, the thickness at an arbitrary position of the substrate 13 ground to a constant thickness is measured by a laser interference thickness measuring device 6, the thick ness at other arbitrary position is ground by a grinder 7 with pressing force being adjusted, and while the grinding and the measurement are repeated, the above first silicon substrate 13 is formed into the thin silicon layer, whose whole surface has a prescribed thickness. Thereby, the SOI substrate having the silicon layer, which has a good crystal quality and has a very thin thickness of 0.1mum or thereabouts, can be formed and a semiconductor element having high performances, such as a high-speed operation and the like, can be formed using the SOI substrate.

Description

[Detailed Description of the Invention] [Summary] Of the methods for manufacturing semiconductor devices, this method relates to a method for forming an SOI substrate. In the method for manufacturing an SOI substrate, the first silicon substrate is ground to a certain thickness, and the first silicon substrate is ground to a certain thickness. Measure the thickness of an arbitrary position on the substrate with a laser interference thickness measuring device, and grind other arbitrary positions with a grinder while adjusting the pressing force, and repeat the grinding and measurement to remove the first silicon substrate. It is characterized in that it includes a step of forming a thin silicon layer with a predetermined thickness over the entire surface.

[Industrial Application Field] The present invention relates to a method of forming an SOI substrate among methods of manufacturing a semiconductor device.

In recent years, the degree of integration and functionality of ICs has been increasing, and ICs are playing a role as the core of technology in all industries.

Conventionally, IC process technology has focused on two-dimensional high integration through microfabrication, but due to the limitations of lithography, there is a demand for three-dimensional ICs in which semiconductor layers are stacked three-dimensionally. Another reason is that the high-density devices that have been formed have added capacitance, making it difficult to operate at high speed.

On the other hand, if a semiconductor layer is formed on an insulating layer, the capacitance will be reduced and higher speeds will be possible.
A semiconductor device with an SOI structure is being considered, and in addition to high-speed operation, a semiconductor device with an SOI structure has
It also has advantages in favor of high temperature operation. However, SOI
An SOI substrate for forming a structured semiconductor device needs to be as thin as possible and have good crystal quality in order to improve performance and quality.

[Problems to be solved by conventional technology and invention] Previously,
SOS (Silic) is a famous SOI substrate.

However, the sapphire substrate that serves as the base material is very expensive, and although sapphire and silicon have similar crystal structures, they are crystallographically incompatible. This difference caused mismatching of the lattice, so it was not widely used.

Therefore, a method that has been developed in recent years includes SOI substrates that are manufactured using beam annealing. It is produced by thermally oxidizing a silicon oxide (SiOz) film on a silicon substrate, and depositing a polycrystalline silicon film (or amorphous silicon film) thereon by chemical vapor deposition. Next, the polycrystalline silicon film is exposed to, for example, a laser beam (
The polycrystalline silicon film is heated (annealed) and melted by scanning with other electron beams, light beams, etc.), and the polycrystalline silicon film is recrystallized to produce a crystalline silicon film. This is a method of forming a semiconductor element on this crystalline silicon film.

However, the SOI substrate created using this method has the disadvantage that it is difficult to completely convert the polycrystalline silicon film into a single crystal, and therefore semiconductor elements must be formed on a crystalline silicon film that has many defects and is of poor quality. be.

In addition, oxygen ions are implanted deep into the silicon substrate using high acceleration voltage and large current, and then the implanted ions are activated by heat treatment to form SiO□ under the thin semiconductor layer on the surface.
Method for forming film layers (SIMOX method (Separate)
on by Implanted OXygen)) has been proposed. According to this method, the thin semiconductor layer on the surface is a single crystal semiconductor layer created by a pulling method,
Although the crystal quality is supposed to be good, considerable crystal defects are generated during ion implantation, making it difficult to obtain a semiconductor layer with few crystal defects and crystal dislocations.

Therefore, recently, a silicon substrate (silicon wafer) surface is thermally oxidized to produce a Si0g film, the 5iOz films on the two silicon substrate surfaces are pasted together and bonded by heating in oxygen (or nitrogen), and then A so-called bonding method is being considered, in which one silicon substrate is mechanically ground from the other side to form a thin semiconductor layer. This method has the advantage of being able to form a thin semiconductor layer with good crystal quality, but on the other hand, it is difficult to form a uniform and thin semiconductor layer due to the flatness controllability of grinding. ~3
It is difficult to form a semiconductor layer as thin as μm or less.

On the other hand, for semiconductor devices with an SOI structure, forming a semiconductor element with a thickness of 0.2 μm or less has the advantage of reducing additional capacitance, and it is difficult to form a semiconductor device with a thickness of about 2 to 3 μm as described above. Even if the device is formed, there is a drawback that improvement of device characteristics such as high-speed operation is limited.

The present invention proposes a method for manufacturing a semiconductor device with the purpose of eliminating such drawbacks and forming an SOI substrate provided with a thin semiconductor layer of good crystal quality.

[Means for Solving the Problem] The purpose is to bond two silicon substrates consisting of a first silicon substrate and a second silicon substrate with an insulating film interposed therebetween, and to grind the first silicon substrate to form a thin silicon layer. In the method of manufacturing an SOI substrate, the thickness of the first silicon substrate ground to a certain thickness is measured at an arbitrary position using a laser interference thickness measuring device, and
A manufacturing process that includes a step of grinding other arbitrary positions with a grinder while adjusting the pressing force, and forming a thin silicon layer with a predetermined thickness over the entire surface of the first silicon substrate while repeating the grinding and measurement. achieved by the method.

[Function] That is, in the present invention, as an earlier treatment step in the bonding method, grinding is performed to a certain thickness (for example, 2 μm thickness) as in the past, and then, as a later treatment step, the second treatment step is performed while finely adjusting the pressing force. 1 Silicon substrate (thin silicon layer)
The thickness at the grinding position is measured using a laser interferometer. Such measurement and grinding are repeated to form a thin silicon layer (eg, 0.2 μm thick).

In this way, by forming a thin SOI substrate to a submicron thickness and using the SOI substrate, it is possible to create a high-performance semiconductor device such as high-speed operation.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIGS. 4(a) to 4(e) show cross-sectional views of the SOI substrate in the order of the initial processing steps.
) Reference: Boron (B) is diffused or ion-implanted into the surface of the silicon substrate 11 (thickness of several hundred μm) to a thickness of 200 μm.
A zero impurity layer 12 is formed. Further, the impurity concentration of this impurity layer 12 is set to be as high as about 10''/Cl113.

Refer to FIG. 4(b); Next, a silicon layer 13 (silicon single crystal layer) having a thickness of about 2 μm is formed on the impurity layer 12 by vapor phase epitaxial growth.

This silicon substrate 11. Impurity layer 12. silicon layer 13
A substrate consisting of the following will be referred to as a first silicon substrate 1.

See FIG. 4(C); Next, a SOC (spin-on glass) film 3 is applied to the surface of the silicon substrate 1 (the surface of the silicon layer 13), and a second silicon substrate 2 (thickness of several hundred μm) is applied thereon. are firmly pressed together and heated to solidify the SOG film 3. At this time, the SOG film 3 is converted into a SiO□ film by heat treatment.

Refer to FIG. 4(d); next, the entire silicon substrate 11 is removed by etching from the back surface of the first silicon substrate 1 (the exposed surface of the silicon substrate 11). To remove this, first, most of the silicon substrate 11 is etched away using a mixed solution of hydrofluoric acid and nitric acid, and then, when the remaining thickness of the silicon substrate 11 reaches several tens of μm, the silicon substrate is etched using an alkaline etching solution. Remove all 11. Since the impurity layer 12 doped with boron is not etched by an alkaline etching solution, the impurity layer 12 acts as an etching stopper and etching is stopped at the impurity layer 12.

Note that FIG. 4(d) shows an inverted view of FIG. 4(C).

See FIG. 4(e); Next, when heated to a high temperature in an oxidizing atmosphere, the impurity layer 12 containing many impurities is quickly oxidized and S
It becomes an iO□ film, and if only this 5i02 film is etched and removed, the silicon layer 13 is exposed, and in this way,
An SOI substrate is completed in which a silicon layer 13 is provided on the second silicon substrate 2 via an insulating film (SOG film 3).

The above is the first stage processing step in the lamination method, and the above processing method is the same as the conventional processing method and is not a feature of the present invention. In addition to the above method, for example, as described above, 2
A so-called orthodox method for forming an SOI substrate may be used, in which two silicon substrates are pasted and bonded via a Si film, and one silicon substrate is ground to form a thin silicon layer.

However, the thickness of the silicon layer of the SOI substrate after this initial treatment step is approximately 2 μm at most.

Therefore, it is a feature of the present invention that the latter treatment step described below is applied after the first treatment step is completed.

Figure 1 is a diagram of the latter stage processing process for SOI substrates, with symbol 5 in the figure.
1 is an SOI substrate consisting of a second silicon substrate 2, an SOG film 3 (insulating film), and a silicon layer 13; 6 is a laser interference thickness measuring device; 7 is a grinder; 8 is an XY stage; and 9 is a laser interferometer. The SOI substrate 5 is vacuum chucked on an XY stage 8 and can be moved vertically and horizontally while being finely adjusted, and its height position is controlled by a laser interferometer 9. A thickness measuring device 6 and a grinding device 7 are fixed above the SOI substrate 5 on such an XY stage. And x
The Y stage 8 is moved and the measurement and grinding of the surface of the silicon layer 13 on the SOI substrate 5 are repeated.

In this way, the thickness of the silicon layer 13 can be reduced to about 0.1 μm.

FIG. 2 is a diagram illustrating a laser interference thickness measuring device,
A laser light source 61 irradiates the SOI substrate with laser light from an oblique direction, and a CCD detector 62 detects the interference fringes of the laser light reflected and intersecting from the front and back surfaces of the silicon layer 13 of the SOI substrate (the back surface becomes the SOGOsO4 surface). Detect with.

That is, when the interference fringes of the laser beam detected by the CCD detector 62 just disappear by changing the incident angle (θ) of the laser beam from the oblique direction, the silicon layer 13 has a required thickness (for example, 0
．． 2 μm), and a plurality of interference fringes are detected by the CCD detector 62 at the beginning when the silicon layer 13 is thick, but as the grinding progresses, the interference fringes gradually decrease until they just disappear. Stop grinding.

By doing so, the thickness of the silicon layer 13 becomes exactly the required thickness, and in this way, the silicon layer 13 is precisely ground to a thickness of approximately submicron.

Next, FIG. 3 is a diagram illustrating a grinder, in which a grinding surface 71 that contacts the silicon layer 13 (SOI substrate) has an abrasive,
For example, by applying diamond paste. Then, the entire grinder is rotated at a high speed of several thousand rpm for grinding. At this time, a piezo element 72 is placed behind the grinding surface 71, and the silicon layer is ground while finely adjusting the pressure applied to the grinding surface by changing the voltage applied to the piezo element.

This makes it possible to precisely grind the silicon layer to a submicron thickness. In addition to the piezo element, the pressure applied to the grinding surface can be adjusted by filling an elastic body with gas.
A method may be adopted in which the pressure is controlled by letting the gas in and out.

The above is the method for forming an SOI substrate according to the present invention, and by forming it by such a method, an SOI substrate having an extremely thin silicon layer of about 0.1 μm with good crystal quality can be created.

[Effects of the Invention] As is clear from the above embodiments, according to the present invention, an SOI substrate having an extremely thin silicon layer with good crystal quality can be created, and ICs and LSIs using such an SOI substrate can be manufactured.
Semiconductor devices such as
In addition, if they are stacked three-dimensionally, it is possible to achieve higher density and higher integration, thereby achieving even higher performance.

[Brief explanation of drawings]

Figure 1 is a diagram of the later processing steps for SOI substrates, Figure 2 is a diagram explaining the laser interference thickness measuring device, Figure 3 is a diagram explaining the grinder, and Figures 4 (a) to (e) are SOI substrates. FIG. In the figure, 1 is the first silicon substrate, 2 is the second silicon substrate, 3 is the SOG film, 5 is the SO2 substrate, 6 is the laser interference thickness measuring device, 7 is the grinder, 8 is the XY stage, 9 is the laser interference In total, 11 is a silicon substrate, 12 is an impurity layer, 13 is a silicon layer, 61 is a laser light source, 62 is a CCD detector, 71 is a ground surface, and 72 is a piezo element. 7 screens

Claims (1)

[Claims] In a method for manufacturing an SOI substrate, in which two silicon substrates consisting of a first silicon substrate and a second silicon substrate are bonded together via an insulating film, and the first silicon substrate is ground to form a thin silicon layer, the first silicon substrate is ground to a certain thickness. The thickness of the first silicon substrate at an arbitrary position is measured with a laser interference thickness measuring device, and other arbitrary positions are ground with a grinder while adjusting the pressing force, and the grinding and measurement are repeated. A method for manufacturing a semiconductor device, comprising the step of forming a thin silicon layer having a predetermined thickness over the entire surface of the first silicon substrate.